1. Field of the Invention
The present invention relates to a multimode radio communication system and, more specifically, to a multimode radio communication system capable of both indirect terminal-to-terminal communication performed through a base station and direct terminal-to-terminal communication performed not through a base station, for example, peer-to-peer communication.
2. Description of the Related Art
An example of radio communication system, is a pager system wherein a base station having a transmitting antenna of 100 meters or more in height is provided within every service area whose radius is about 30 kilometers. To call a specified terminal (pager) holder in this system, a caller dials the calling number of a pager of the terminal holder by telephone. In response to the calling number, a service center of a pager service company makes all the base stations send forth the calling number at once (or page the calling number). Upon receiving the calling number, the pager gives a calling sound to inform the terminal holder of the call. Recently a pager system capable of transmitting a message as well as a calling number, has been developed, in which not only is a calling sound produced but a message is displayed on a display of a terminal.
In either case, however, since the prior art pager system is directed to one-way communication from a base station to a terminal, another communication system, such as telephone, has to be employed when a called party wishes to respond to a received calling number or a received message. To eliminate this problem, a two-way pager system (or bidirectional pager system) capable of transmitting a response message from a terminal (pager) to a base station, has recently been developed.
According to one proposal of the two-way pager system, the same communication system as that of the normal one-way pager system is used in the down link from the base station to the pager, while a communication system different from that of the one-way pager system is adopted in the up link from the pager to the base station, as described in U.S. Pat. No. 5,335,246. The two-way radio communication between two pagers is achieved as follows: A transmission message is transmitted from one of the pagers to a service center of a pager service company using an up link through a base station. The service center makes all base stations transmit the transmission message at once (or page) through the down links. Upon receiving the transmission message, the other pager transmits a response message to the base station through the up link and then to the service center, as described above. The service center returns the response message to the former pager via the base station using the down link.
Moreover, there are a portable telephone system and a mobile telephone system as other radio communication systems for achieving two-way communication.
The foregoing communication systems are all based on the premise of the use of service provider infrastructure equipment such as base stations and telephone lines. Therefore, even when two terminals for two-way communication are close to each other and no infrastructure equipment is required, a signal always has to be transmitted via both a base station and a service center, with the result that the time for communication between the two terminals is lengthened and the infrastructure equipment runs to waste.
Accordingly, it is an object of the present invention to provide a multimode radio communication system capable of terminal-to-terminal communication, i.e., peer-to-peer communication, performed without using any infrastructure equipment, as well as two-way radio communication performed using infrastructure equipment.
A related object of the present invention is to provide a multimode radio communication terminal capable of terminal-to-terminal communication, i.e., peer-to-peer communication, performed without using any infrastructure equipment, as well as two-way radio communication performed using infrastructure equipment.
A further object of the present invention is to provide a base station used for a multimode radio communication system capable of terminal-to-terminal communication, i.e., peer-to-peer communication, performed without using any infrastructure equipment, as well as two-way radio communication performed using infrastructure equipment.
A still further object of the present invention is to provide a multimode radio communication method capable of terminal-to-terminal communication, i.e., peer-to-peer communication, performed without using any infrastructure equipment, as well as two-way radio communication performed using infrastructure equipment.
According to the present invention, there is provided a multimode radio communication system comprising a base station connected to a wire communication network, the base station transmitting a sync signal; and a plurality of radio communication terminals wirelessly connected to said base station, said plurality of radio communication terminals being operated in synchronization with the sync signal transmitted from said base station, and a first radio communication terminal of said plurality of radio communication terminals indirectly communicating with a second radio communication terminal thereof through said base station or directly communicating with the second radio communication terminal in synchronization with the sync signal.
According to the present invention, there is provided a radio communication terminal comprising means for receiving a sync signal transmitted from a base station connected to a wire communication network; and means for directly communicating with another radio communication terminal by a peer-to-peer communication system in synchronization with the sync signal without using the base station.
According to the present invention, there is provided a base station communicating with radio communication terminals, comprising means for receiving signals from the radio communication terminals; means for detecting positions of the radio communication terminals based on the signals received by said receiving means; means for producing a link prediction parameter indicating whether or not there is a peer-to-peer communication between the radio communication terminals based on the positions of the radio communication terminals; and means for transmitting the link prediction parameter to the radio communication terminals.
According to the present invention, there is provided a radio communication method for a radio communication terminal, comprising steps of receiving a sync signal transmitted from a base station; and executing a peer-to-peer communication with another radio communication terminal in synchronism with the sync signal without using the base station.
Since the multimode radio communication system of the present invention allows communication without using infrastructure equipment as well as communication using infrastructure equipment, the infrastructure equipment can effectively be utilized, and new infrastructure equipment is not always required. The use of infrastructure equipment may impose restrictions such as communication speed and communication capacity on the system. These restrictions can be removed if communication is executed without using any infrastructure equipment.
Additional objects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.